Subxiphoid connective lesion ablation system and method

ABSTRACT

Instrument and systems for applying ablative energy to epicardial tissue via a subxiphoid access surgical approach. The instrument has a head assembly sized and shaped for a subxiphoid surgical approach to a patient&#39;s heart and defines a contact face. The head assembly includes a paddle body, a first ablation electrode, and a second ablation electrode. The ablation electrodes are coupled to the paddle body in a spaced apart, spatially-fixed fashion. The ablation electrodes are exteriorly exposed at the contact face. A tubular member extends from the head assembly and maintains wiring connected to the ablation electrodes. The instrument is manipulable to locate the contact face on epicardial tissue of a patient&#39;s heart via a subxiphoid surgical approach, such as between the left and right pulmonary vein junctions of the posterior left atrium.

BACKGROUND

Atrial fibrillation is a common cardiac condition in which irregularheart beats cause a decrease in the efficiency of the heart, sometimesdue to variances in the electrical conduction system of the heart. Insome circumstances, atrial fibrillation poses no immediate threat to thehealth of the individual suffering from the condition, but may, overtime, result in conditions adverse to the health of the patient,including heart failure and stroke. In the case of many individualssuffering from atrial fibrillation, symptoms affecting the patient'squality of life may occur immediately with the onset of the condition,including lack of energy, fainting, and heart palpitations.

In some circumstances, atrial fibrillation may be treated with drugs orthrough the application of defibrillation shocks. In cases of persistentatrial fibrillation, however, surgery may be required. The surgicalprocedure originally developed to treat atrial fibrillation is known asa “MAZE” procedure where the atria are surgically cut apart alongspecific lines and sutured back together. While possibly effective, theMAZE procedure tends to be complex and may require highly invasiveaccess to the thorax. In order to reduce the need to open the atria,thermal ablation tools have been developed to produce lines of inactivetissue along the heart wall that mimic the MAZE procedure. This is mostcommonly done using radio frequency (RF) ablation devices to ablate andelectrically isolate tissue that may be responsible for the improper orelectrical conduction that causes atrial fibrillation.

A variety of cardiac ablation devices and methods are currentlyavailable for treatment of atrial fibrillation and other arrhythmias.With some systems, endocardial tissue is contacted and ablated, forexample via a catheter-based ablation instrument. Conversely, epicardialtissue can be ablated. Conventionally, cardiac surgeons access theepicardial tissue via a standard sternotomy. More recently, certainatrial fibrillation treatment procedures have been advanced that entailablating small segments of epicardial tissue on a minimally invasivebasis, such as via a single or bilateral thoractomy approach. Forexample, the junctions of pulmonary veins with the left atrium have beenidentified as being a common area where atrial fibrillation-triggeringfoci reside. For many patients, then, atrial fibrillation can beeffectively treated by ablating only a portion of the complete MAZEpattern, such as at the pulmonary vein/left atrium junction. Moreparticularly, a viable cardiac arrhythmia treatment technique entailsablating an epicardial lesion into the posterior left atrium around orcircumscribing the left pulmonary veins and another epicardial lesionencircling the right pulmonary veins. These island ablation lesions canbe formed on a minimally invasive basis via bilateral thoractomy usingclamp-type ablation instruments, for example a surgical ablation deviceavailable under the trade name Cardioblate® Gemini™ available fromMedtronic, Inc. While well-accepted, the bilateral thoractomy surgicalapproach may require the surgeon to perform various additionalprocedures, such as dissection of pericardial reflections, in order tolaterally access the posterior left atrium ablation site(s).Additionally, while the pulmonary vein island ablation represents only asmall portion of a complete MAZE procedure, additional epicardiallesions along the left atrium may be beneficial to prevent re-entry ofan unwanted sympathetic pathway.

In light of the above, a need exists for systems and methods of makingepicardial lesions on selected cardiac locations on a minimally invasivebasis, such as along the posterior left atrium via a subxiphoid surgicalapproach.

SUMMARY

Some aspects in accordance with principles of the present disclosurerelate to an ablation instrument for applying ablative energy toepicardial tissue via a subxiphoid access surgical approach to treatcardiac arrhythmia. The ablation instrument includes a head assembly, atubular member, and wiring. The head assembly is sized and shaped for asubxiphoid surgical approach to a patient's heart and defines a contactface. Further, the head assembly includes a paddle body, a firstelongated ablation electrode, and a second elongated ablation electrode.The paddle body defines an outer perimeter of the head assembly. Thefirst and second ablation electrodes are coupled to the paddle body in aspaced apart, electrically isolated fashion such that a spatialrelationship between the ablation electrodes is fixed. The ablationelectrodes are exteriorly exposed at the contact face of the headassembly, and are maintained entirely within the outer perimeter. Thetubular member extends from the head assembly. The wiring iselectrically connected to the first and second ablation electrodes fordelivering ablative energy thereto, and extends through the tubularmember. With this construction, the ablation instrument is manipulatableto locate the contact face at epicardial tissue of a patient's heart viaa subxiphoid surgical approach. For example, the ablation electrodes canbe located on epicardial tissue of the posterior left atrium between theleft and right pulmonary vein junctions via a subxiphoid surgicalapproach. In some embodiments, the head assembly further include one ormore auxiliary electrodes maintained between the ablation electrodes andavailable for performing various pacing and/or sensing procedures. Inother embodiments, the paddle body forms suction regions about each ofthe ablation electrodes. In other, possibly related embodiments, thehead assembly incorporation irrigation delivery features for supplyingan irrigation liquid (e.g., saline) that effectuates cooling of theablation electrodes; the so-delivered liquid can then be evacuated fromthe head assembly through the suction regions.

Yet other aspects of the present disclosure relate to an ablation systemfor applying ablative energy to epicardial tissue via a subxiphoidaccess surgical approach to treat cardiac arrhythmia. The ablationsystem includes the ablation instrument as described above and a powersource for providing ablative energy to the ablation electrodes. In someconstructions, the system further includes a controller electronicallyconnected to auxiliary electrodes carried by the paddle body, with thecontroller being programmed to perform pacing and sensing procedures viathe auxiliary electrodes to evaluate effectiveness of a conductive blocklesion pattern.

Yet other aspects in accordance with principles of the presentdisclosure relate to a method for ablating epicardial tissue of apatient to treat cardiac arrhythmia. The method includes inserting anablation head assembly of an ablation instrument through a subxiphoidaccess incision in a chest of the patient. The head assembly defines acontact face and includes a paddle body and two elongated ablationelectrodes. The ablation electrodes are coupled to the paddle body in aspaced apart, electrically isolated fashion such that a spatialrelationship between the first and second ablation electrodes is fixed.The ablation electrodes are exteriorly exposed relative to the contactface and entirely within an outer perimeter defined by the paddle body.Following subxiphoid insertion, the head assembly is directed to bringthe ablation electrodes into contact with the epicardial tissue.Ablation energy is then applied to the heart tissue via the ablationelectrodes to destroy one or more conduction pathways in the heart. Insome embodiments, the method is performed as part of a partial MAZEprocedure in which first and second island lesion ablation patterns areformed about junctions of the right pulmonary veins and the leftpulmonary veins with the left atrium of the patient's heart. With thisin mind, the ablation lesions formed by the ablation electrodesinterconnect the island lesions in forming a conductive block along theposterior left atrium. In other embodiments, conductive block testing isperformed via the head assembly immediately following the formation ofthe connective lesions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, with portions shown in block form, of anablation system useful for applying ablative energy to epicardial tissuevia a subxiphoid surgical approach in accordance with principles of thepresent disclosure;

FIG. 2 is an exploded, perspective view of a surgical instrumentcomponent of the system of FIG. 1;

FIG. 3 is an enlarged, perspective view of a head assembly portion ofthe instrument of FIG. 2;

FIG. 4 is a top plan view of the head assembly of FIG. 3;

FIG. 5 is an exploded, perspective view of the head assembly of FIG. 3,along with other components of the instrument of FIG. 2;

FIG. 6A is a top plan view of a head component of the head assembly ofFIG. 5;

FIG. 6B is a bottom plan view of the head component of FIG. 6A;

FIG. 7 is a exploded, perspective view illustrating assembly of variouscomponents of the head assembly of FIG. 3;

FIG. 8 is a simplified representation of various anatomy of a patient'schest;

FIG. 9A is a posterior view of a human heart;

FIG. 9B is a posterior view of the human heart of FIG. 9A andillustrating island lesion patterns formed about junctions betweenpulmonary veins and left atrium;

FIGS. 10A-10E illustrate methods in accordance with the presentdisclosure including the ablation system of FIG. 1 employed to completea portion of a conductive block ablation pattern on the posterior leftatrium via a subxiphoid surgical approach; and

FIGS. 11A-11R are simplified plan views of other head assemblies inaccordance with the present disclosure and useful with the ablationinstrument of FIG. 2.

DETAILED DESCRIPTION

One embodiment of an ablation system 20 in accordance with aspects ofthe present disclosure and useful for applying ablative energy toepicardial tissue via a subxiphoid surgical approach is shown in FIG. 1.The ablation system 20 includes an ablation instrument 22 and a powersource 24. Optionally, additional components can be provided with theablation system 20, such as a controller 26 (provided with or apart fromthe power source 24), a vacuum or negative pressure source 28, a liquidsource 30, and an indifferent or grounding electrode 32. Details on thevarious components are provided below. In general terms, however, theinstrument 22 includes a head assembly 40 sized and shaped for accessingepicardial tissue of a patient's heart (e.g., along the posterior leftatrium between the left and right pulmonary veins junctions) via asubxiphoid incision in the patient's chest. The head assembly 40 carriesvarious electrodes that, when energized via the power source 24, ablatecontacted cardiac tissue to form a corresponding, desired lesionpattern. The controller 26 optionally facilitates performance of varioustesting procedures with the head assembly 40, such as pace/senseprotocols. The optional vacuum source 28 can be employed to draw tissueinto more intimate contact with the electrodes carried by the headassembly 40, whereas the optional liquid source 30 can facilitatecooling of the head assembly 40. Regardless, the ablation system 20, andin particular the instrument 22, can be employed on a minimally invasivebasis via a subxiphoid surgical approach, uniquely serving to complete aportion of a MAZE lesion pattern, such as interconnecting or otherwisecompleting a conduction block between island lesion patterns formed onthe posterior left atrium about the left and right pulmonary veins.

With additional reference to FIG. 2, the ablation instrument 22 includesthe head assembly 40, a tubular member 42, and a handle assembly 44(referenced generally). The tubular member 42 supportively connects thehead assembly 40 with the handle assembly 44, and provides a protectiveconduit for wiring and tubing or similar structures (e.g., a suctiontube, liquid tube, etc.), to and from the head assembly 40. The handleassembly 44, in turn, promotes handling and operation of the instrument22, including connecting the instrument 22 with the power source 24(FIG. 1) and facilitating user control over various operations (e.g.,delivery of negative pressure and/or cooling liquid to the head assembly40).

The head assembly 40 is shown in greater detail in FIG. 3, and generallyincludes a paddle body 50, a first elongated ablation electrode 52, anda second elongated ablation electrode 54. The ablation electrodes 52, 54are mounted to the paddle body 50 in a spaced apart, fixed manner, withthe paddle body 50 optionally forming suction regions or pods about theablation electrodes 52, 54, respectively. The paddle body 50 canmaintain additional components, such as cooling liquid delivery tubingand/or first and second auxiliary electrodes 56, 58 (e.g., forperforming pacing and/or sensing procedures as described below).

The paddle body 50 can assume various forms conducive to subxiphoidinsertion and for maintaining the ablation electrodes 52, 54. In moregeneral terms, and as reflected in FIG. 4, the paddle body 50 defines anouter perimeter 60 of the head assembly 40, including a leading end 62,a trailing end 64, and opposing sides 66, 68. Connection of the headassembly 40 with the tubular member 42 (FIG. 2) is provided at thetrailing end 64, with the leading end 62 serving as a distal-most end ofthe instrument 22 (FIG. 2). The leading and trailing ends 62, 64 combineto define a length L of the head assembly 40. The opposing sides 66, 68combine to define a maximum width W of the head assembly 60. With thesedesignations in mind, a shape of the outer perimeter 60, as well asdimensions of the length L and the maximum width W are sized forsubxiphoid insertion, as well as, in some embodiments, to nest betweenthe left and right pulmonary veins at the epicardial surface of theposterior left atrium of an adult human heart. As made clear below, awidth of the paddle body 50 is a function of the lengths of the ablationelectrodes 52, 54, with these lengths being selected, in someembodiments, to traverse the lateral distance between the junction ofthe left pulmonary veins with the left atrium and the junction of theright pulmonary veins with left atrium at superior and inferiorlocations. With these embodiments, then, a width of the paddle body 50generally coincides with the typical left atrium pulmonary vein junctionspacing. Other procedures, and thus other shapes and/or sizes, are alsoenvisioned. While the paddle body 50 is reflected as having a generallytrapezoidal perimeter shape, other configurations are also acceptable.For example, while the paddle body 50 is shown as tapering in width fromthe trailing end 64 to the leading end 62, other shapes are alsoenvisioned (e.g., a more rectangular shape, circular shape, etc.).Regardless, to promote subxiphoid insertion in combination with spanningthe pulmonary vein junction distance at the left atrium of a typicaladult human heart, the maximum width W of the paddle body 50 can be inthe range of 3-7 cm, and the length L can be in the range of 4-12 cm.

The paddle body 50 can be constructed as a single, homogeneous piece.Alternatively, a mere complex assembly can be utilized. For example,FIG. 5 illustrates that in some embodiments, the paddle body 50 includesa base 70 and a head 72. With this but one acceptable construction, thehead 72 is sized and shaped for assembly to the base 70, with the head72 providing various features adapted for mounting of the ablationelectrodes 52, 54 as described below.

The base 70 can include or define a neck region 80, a floor 82, and asidewall 84. A trough 86 is formed along the neck region 80 and extendsto a chamber 88 formed in the floor 82. The trough 86 and the chamber 88provide an isolated pathway for various wires and/or tubes upon assemblyof the head 72 to the base 70. A suction channel 90 is also formed inthe floor 82, and provides a sealed passageway for application negativepressure upon final assembly. In this regard, a track 92 can be formedin the floor 82 about the suction channel 90 and configured to sealinglyreceive a corresponding feature (e.g., a similarly shaped rib) providedwith the head 72. Other assembly configurations are also acceptable thatmay or may not include the track 92. Finally, the sidewall 84 projectsfrom an outer perimeter of the floor 82, serving to define the outerperimeter 60 (FIG. 4) of the paddle body 50. The base 70 can be formedfrom various surgically safe materials, and in some embodiments is amolded material that is free of sharp corners for atraumatic insertioninto the human body. For example, the base 70 can be a relatively softpolymer such as 72 Durometer urethane. A wide variety of othersurgically safe materials (e.g., metals) are also acceptable.

The head 72 can include a neck region 100 and a platform 102. The neckregion 100 is sized for mating with the neck region 80 of the base 70.Similarly, the platform 102 is sized and shaped for assembly to thefloor 82, nesting within the sidewall 84. In some constructions, theplatform 102 defines a leading segment 104 and a trailing segment 106.As shown, the leading segment 104 can be recessed below the trailingsegment 106 (relative to the orientation of FIG. 5). Regardless, theleading segment 104 forms a first slot 108 and a second slot 110. Withadditional reference to FIG. 6A, the first slot 108 is generally sizedand shaped in accordance with (e.g., slightly larger than) the firstablation electrode 52, whereas the second slot 110 is sized and shapedto receive the second ablation electrode 54. To facilitate mounting ofthe ablation electrodes 52, 54 within the respective slots 108, 110, theleading segment 104 can include or form one or more fingers 112, 114within each of the slots 108, 110, with the fingers 112, 114 beingconfigured to receive and support a segment of the correspondingablation electrode 52, 54. In some constructions, the fingers 112, 114are adapted to frictionally retain the corresponding ablation electrode52, 54 (e.g., press-fit mounting), although other mounting techniquesare also envisioned (e.g., adhesive bond). With the but one acceptableconstruction of FIG. 6A, one or more of the fingers 112, 114 associatedwith each of the slots 108, 110 can form a longitudinal through hole(referenced generally at 116 for one of the fingers 112 of the firstslot 108 and for one of the fingers 114 of the second slot 110) thatfacilitates the passage of wiring from the corresponding ablationelectrode 52 or 54 as described below.

An irrigation hole 120 a and/or a suction aperture 122 a can optionallybe formed in the leading segment 104, fluidly open to the first slot108; a similar irrigation hole 120 b and/or suction aperture 122 b canbe formed in, and fluidly open to, the second slot 110. Where provided,the irrigation holes 120 a, 120 b provide a passageway for a liquiddelivery tube (not shown) into the corresponding slot 108, 110. Theoptional suction apertures 122 a, 122 b fluidly connect a negativepressure source to the corresponding slot 108, 110. For example, as bestshown in FIG. 6B, the suction apertures 122 a, 122 b are fluidly open toa rear face 124 of the head 72. A rib 126 projects from the rear face124, and surrounds the suction apertures 122 a, 122 b, as well as achannel 128. The rib 126 is sized to be received within the track 92(FIG. 5) of the base 70 (FIG. 5), with the channel 128 being fluidlyconnected to a bore 130 (hidden in FIG. 6B, but shown generally in FIG.5) in a thickness of the neck region 100. Upon assembly of the base 70and the head 72 and connection of vacuum tubing (not shown) to the bore130, negative pressure (e.g., generated by the vacuum source 30 (FIG.1)) through the bore 130 is applied to the channel 128 of the head 72.The suction channel 90 (FIG. 5) of the base 70 is fluidly connected tothe suction channel 128 of the head 72, as well with the suctionapertures 122 a, 122 b, thereby delivering negative pressure to theslots 108, 110 (FIG. 6A). Assembly of the rib 126 within the track 92fluidly isolates the negative pressure pathway.

Returning to FIGS. 5 and 6A, in some embodiments, the head 72 is furtheradapted to receive one or more other components in addition to theablation electrodes 52, 54. For example, with embodiments in which theoptional auxiliary electrodes 56, 58 are provided, the leading segment104 can further form or define first and second auxiliary holes 140,142. The holes 140, 142 are generally configured to facilitate passageof wiring (not shown) extending from the corresponding auxiliaryelectrodes 56, 58, and serve to desirably locate the auxiliaryelectrodes 56, 58 relative to the ablation electrodes 52, 54 upon finalassembly. In particular, and for reasons made clear below, the auxiliaryelectrodes 56, 58 are positioned between the first and second ablationelectrodes 52, 54 and at a sufficient distance relative to one anotherto perform desired operations, such as pacing and/or sensing.

With specific reference to FIG. 5, the paddle body 50 can furtherinclude, in some constructions, an optional tissue contact member 150that is mounted to the leading segment 104 of the head 72. The tissuecontact member 150 is generally constructed for atraumatic interfacewith cardiac tissue, and forms or defines a first skirt 152 and a secondskirt 154. The skirts 152, 154 project upwardly from a panel 156(relative to the orientation of FIG. 5), with the first skirt 152 beinggenerally sized and shaped in accordance with the first ablationelectrode 52, and the second skirt 154 being generally sized and shapedin accordance with the second ablation electrode 54. As described below,the skirts 152, 154 establish suction regions or pods 158, 160 relativeto the corresponding ablation electrodes 52, 54, with the panel 156forming openings 162, 164 through a thickness thereof and through whichnegative pressure established at the first and second suction apertures122 a, 122 b (FIG. 6A), respectively, is conveyed to the suction regions158, 160. With configurations in which the auxiliary electrodes 56, 58are provided, the tissue contact member 150 forms or defines first andsecond auxiliary openings 166, 168 configured to maintain acorresponding one of the auxiliary electrodes 56, 58.

In some constructions, the tissue contact member 150 is formed by afirst, support layer 170 and a second, skirt layer 172. The supportlayer 170 generally reinforces the tissue contact member 150, and can beformed of a relatively stiffer material than that of the skirt layer172. The skirt layer 172 can be over-molded to the support layer 170,and defines the first and second skirts 152, 154. For example, in someembodiments, the support layer 170 is a 72 Durometer urethane material,whereas the skirt layer 152 is a 42 Durometer polyurethane material.Other materials and/or constructions are also acceptable. In yet otherembodiments, one or both of the skirts 152, 154 can be integrally formedor defined by the head 72. Where provided, the skirts 152, 154 can becompliant or resiliently deflectable at expected negative pressurelevels (e.g., in the range of −100 mm Hg to −400 mm Hg) to promoteatraumatic interface with contacted cardiac tissue. That is to say, theskirts 152, 154 will somewhat collapse (e.g., elastically) in thepresence of expected negative pressure levels to ensure consistent,intimate contact of the tissue to be ablated with the correspondingablation electrode 52, 54, In yet other embodiments, one or both of theskirts 152, 154 can be omitted.

The first ablation electrode 52 can assume various forms appropriate fordelivering RF energy at sufficient levels for ablating contactedepicardial tissue. For example, the first ablation electrode 52 can bean electrically conductive metal such as 304 stainless steel. In someembodiments, the first ablation electrode 52 is a solid shaft or wire;in other embodiments a tubular construction can be employed. Regardless,the first ablation electrode 52 is generally elongated (e.g., having alongitudinal length at least three times greater than a width ordiameter thereof), and can have a slight curvature along an intermediatesegment 174 thereof. Further, opposing ends 176, 178 of the firstablation electrode 52 can extend inwardly relative to the intermediatesegment 174 as shown. Other shapes are also acceptable. One or moresensing-type components (e.g., thermocouple, transistor, etc.) canoptionally be assembled to or formed by the first ablation electrode 52.For example, separate thermocouples (not shown) are provided at each ofthe ends 176, 178.

The second ablation electrode 54 is constructed of materials similar tothose described above with respect to the first ablation electrode 54,and in some embodiments is a solid metal wire or shaft. With the but oneacceptable construction of FIG. 5, the second ablation electrode 54 isgenerally elongated, having a relatively continuous, planar curveextending between opposing ends 180, 182 and defining a radius ofcurvature that is less than that of the intermediate segment 174 of thefirst ablation electrode 52. Other shapes are also envisioned. Forexample, the ablation electrodes 52, 54 can have identical shapes.Regardless, one or more sensing elements (e.g., thermocouple,transistor, etc.) can be provided with the second ablation electrode 54,for example at one or both of the ends 180, 182.

The optional auxiliary electrodes 56, 58 can be identical, and canassume any conventional form appropriate for performing the pacingand/or sensing protocols described below. Thus, the auxiliary electrodes56, 58 can be electrically conductive metal buttons.

Construction of the head assembly 40 includes mounting of the ablationelectrodes 52, 54, the auxiliary electrodes 56, 58, and the tissuecontact member 150 to the head 72 as shown in FIG. 7. The first ablationelectrode 52 is mounted within the first slot 108 via the fingers 112.In this regard, a primary wire 190 is electrically connected to thefirst ablation electrode 52, and is threaded through the through hole116 in one of the fingers 112. One or more secondary wires 192 can alsobe provided, and electrically connected to sensing elements (e.g.,thermocouples) carried by the first ablation electrode 52. Whereprovided, the secondary wires 192 are threaded through holes 116 ofcorresponding ones of the fingers 112. The second ablation electrode 54is similarly mounted within the second slot 110, with a primary wire 194and optional secondary wires 196 (e.g., with embodiments in which thesecond ablation electrode 54 carries thermocouples or other sensing-typecomponents) electrically connected to the second ablation electrode 54and passed through holes 116 in corresponding ones of the fingers 114.The optional first auxiliary electrode 56 is electrically connected to afirst sensor wire 198 that in turn is inserted through the firstauxiliary opening 166 in the tissue contact member 150 and the firstauxiliary hole 140 (hidden in FIG. 7) in the head 72. Similarly, asecond sensor wire 200, otherwise electrically connected to the secondauxiliary electrode 58, is passed through the second auxiliary opening168 in the tissue contact member 150 and the second auxiliary hole 142in the head 72. Finally, the tissue contact member 150 is mounted to thehead 72 such that the first skirt 152 surrounds the first ablationelectrode 52 and the second skirt 154 surrounds the second ablationelectrode 54.

Though not shown in FIG. 7, liquid lines or tubes 204, 206 (FIG. 5) arelocated along the rear face 124 (FIG. 6B) of the head 72 and insertedinto respective ones of the irrigation holes 120 a, 120 b (best shown inFIG. 6A) so as to be fluidly open to the corresponding slot 108, 110.Similarly, a vacuum line or tube (not shown) is fluidly connected to thebore 130. The head 72 is then assembled to the base 70 (FIG. 5). Thevarious wires 190-200 and tubes 204, 206 are fed through the chamber 88and along the trough 86 for subsequent insertion through the tubularmember 42.

Final construction of the head assembly 40 with the tubular member 42 isshown in FIG. 3. The first and second ablation electrodes 52, 54 areexteriorly exposed relative to a contact face 210 of the head assembly40. As used in this specification, the “contact face” is in reference toa side or surface of the head assembly 40 intended to be brought intocontact with tissue to be ablated. While the skirts 152, 154 projectoutwardly beyond the corresponding ablation electrodes 52, 54, thesuction regions or pods 158, 160 are exteriorly open such that theablation electrodes 52, 54 are exteriorly exposed and can be broughtinto ablative contact with tissue otherwise abutting the contact face210. FIG. 3 further reflects that the optional auxiliary electrodes 56,58 are exteriorly exposed at the contact face 210, and are locatedbetween the ablation electrodes 52, 54. As made clear below, during useof the ablation instrument 22, the ablation electrodes 52, 54 areoperable to complete a desired conductive block pattern. By locating theauxiliary sensing electrodes 56, 58 between the ablation electrodes 52,54, the ablation instrument 22 can further be employed to evaluate acompleteness of the so-formed conductive block pattern immediately afterthe ablation steps are complete and without movement of the contact face210 relative to the target site.

As described above, the paddle body 50 is sized and shaped for accessingvarious anatomical locations, such as epicardial tissue at the posteriorleft atrium, via a subxiphoid surgical approach. The size and shape ofthe paddle body 50 facilitates this implementation. As such, while theablation electrodes 52, 54 are generally elongated, the terminal endsthereof do not project beyond the outer perimeter 60 of the paddle body50. Instead, the ablation electrodes 52, 54 are arranged within afootprint of the paddle body 50, and thus are readily positioned at adesired target site via a subxiphoid surgical approach, for examplealong epicardial tissue of the posterior left atrium at superior andinferior aspects of the pulmonary vein junction spacing.

Returning to FIG. 5, the tubular member 42 is generally configured tohouse various lines and wiring extending from the head assembly 40. Ingeneral terms, the tubular member 42 has an outer diameter appropriatefor subxiphoid placement, and a length sufficient to deliver the headassembly 40 to the posterior left atrium via a subxiphoid incision. Insome constructions, the tubular member 42 is a corrugated tube, such asa stainless steel corrugated tube. Thus, the tubular member 42 is atleast somewhat malleable, capable of self-maintaining a desired shape. Adistal end 212 of the tubular member 42 is configured for attachment tothe head assembly 40, for example via one or more internal shoulders 214(referenced generally) configured to be captured by a correspondingfeature of the paddle body neck regions 80, 100. Other mountingconfigurations are equally acceptable. A proximal end 216 of the tubularmember 42 is similarly constructed for mounting to the handle assembly44 (FIG. 2). Regardless, a lumen 218 is defined through the tubularmember 42, serving as a conduit for various components extending fromthe head assembly 40.

With reference to FIG. 2, the handle assembly 44 can assume variousforms, and in some constructions includes a housing 220 (referencedgenerally), an actuator mechanism 222, and a connector 224. In generalterms, the housing 220 is coupled to the tubular member 42, andmaintains the actuator mechanism 222. The actuator mechanism 222, inturn, operates to control fluid flow through the liquid tubes 204, 206and the vacuum line or tube (not shown). Finally, the connector 224extends from the housing 220 and facilitates connection to the powersource 24/controller 26 (FIG. 1), and the vacuum source 28 (FIG. 1), andthe liquid source 30 (FIG. 1).

The housing 220 is sized and shaped for convenient handling by a user.In some embodiments, the housing 220 is formed by first and second shellportions 230, 232 that are mateable to one another in a manner capturingthe proximal end 216 of the tubular member 42. The actuator mechanism222 includes a lever or trigger 240 that is pivotably coupled to thehousing 220. A catch 242 captures the liquid tubes 204, 206 and thevacuum tube (not shown) relative to an engagement feature 244 of thelever 240. In a normal or first position of the lever 240 relative tothe housing 220, the engagement feature 244 applies a pinching force tothe liquid tubes 204, 206 and the vacuum tube, thereby preventing fluidflow therethrough. Conversely, in a second, user-actuated position ofthe lever 240 relative to the housing 220, the engagement feature 244 isspaced from the liquid and vacuum tubes 204, 206 to permit fluid flowtherethrough. A biasing member 246 (e.g., spring) biases the lever 240to the normal position relative to the housing 220. Other fluid flowcontrol mechanisms can alternatively be employed. Further, while in someembodiments the delivery of power to the ablation electrodes 52, 54 iscontrolled by an actuator (not shown) apart from the handle assembly 44(e.g., a footswitch), in other constructions the handle assembly 44 canfacilitate user control over application of ablative energy.

The connector 224 can be an extruded tubing-type component, providingone or more passageways 250 through which various items can pass. Forexample, a first passageway 250 a serves as a cabling pathway andthrough which the various wires (not shown) extending from the headassembly 40 as described above are maintained. A second passageway 250 bserves as an aspiration or negative pressure pathway, and is fluidlyconnected to the vacuum line (not shown) described above. Finally, athird passageway 250 c serves as a liquid delivery conduit and throughwhich liquid irrigation (e.g., saline) is delivered to the liquid tubes204, 206.

The handle assembly 44 can optionally incorporate one or more additionalfeatures. For example, an indicator device 260 can be maintained by thehousing 220, and includes, for example, a light source 262 (e.g., an RGBLED) and a lens 264. As described below, the indicator device 260 iselectronically connected to the controller 26 (FIG. 1) and operates toprovide a user with a visual indication of various procedural parameters(e.g., the indicator device 260 emits a green colored light whenconduction block has been achieved, and a red colored light whenconduction block criteria have not been met).

Returning to FIG. 1, the power source 24 can assume various forms, andgenerally includes an RF energy generator appropriate for supplyingsufficient energy to ablate epicardial tissue. For example, thegenerator provided with the power source 24 can be an ablation energygenerator available from Medtronic, Inc., under the trade nameCardioblate® Model 68000 Generator.

In addition to the generator, the power source 24 can include or beoperatively connected to the controller 26 that includes a computer orother logic circuitry capable of effectuating one or more of the testingprocedures or protocols described below (e.g., hardware or softwareprograms). For example, the controller 26 can be akin to a model2090/2290 Programmer/Analyzer available from Medtronic, Inc. As usedthrough this specification, then, reference to a “controller” includes asingle controller or two or more electronically linked controllers orcomputing devices.

With cardiac ablation procedures in accordance with some aspects of thepresent disclosure, radio frequency energy is employed, with theablation instrument 22 (and the corresponding power source 24) adaptedto deliver a maximum of 30 watts of power at 500 kilohertz for twominutes. Other ablation parameters (e.g., energy type, voltage, current,frequency, etc.), can alternatively be employed. The controller 26 canbe programmed with one or more algorithms known in the art formonitoring power and/or impedance values at the ablation electrodes 52,54 throughout an ablation procedure for safety purposes.

One optional testing protocol provided with the controller 26 is apacing procedure. In general terms, the heart is “paced” by a lowfrequency signal from an external energy source to control the beatingrate of the heart. Typically, a beating rate of 20-30 beats per minutefaster than the patient's then-current heart rate is chosen. When theheart rate is controlled by the external energy source, the pacing isconsidered to have “captured” control of the heart. With this in mind,the controller 26 can be programmed to perform a pacing protocol bycausing stimulating or pacing energy to be delivered to the auxiliaryelectrodes 56, 58, effectively electrically coupling the auxiliaryelectrodes 56, 58 so that energy passes between the auxiliary electrodes56, 58. In this regard, the controller 26 can deliver pacing energy fromthe power source 24. Alternatively, the pacing energy can be generatedby an auxiliary energy source (not shown), such as an external temporarypacemaker (e.g., an external temporary pacemaker available fromMedtronic, Inc., under Model 5348 or Model 5388).

In some configurations, a pacing threshold is less than 10 mA at 0.5msec using Medtronic's Model 5388 temporary pacemaker. In the context ofuse on cardiac tissue, if the heart does not respond to an initialpulsed current, the current may be increased until the heart rateresponds to the stimulation. The stimulation or pacing energy can beincreased or decreased to attain capture where desired. For example, apacing amplitude in the range of 0.1-10.0 volts and a current in therange of 0.1-24 milliamp can be provided.

Yet another optional non-ablation procedure available with someembodiments of the controller 26 is a sensing protocol in whichelectrical activity propagating along cardiac tissue is monitored orsensed. With the auxiliary electrodes 56, 58 placed into contact withdesired cardiac tissue, the controller 26 effectively establishes anelectrical coupling between the auxiliary electrodes 56, 58, for exampleby operating the first auxiliary electrode 56 as a positive pole and thesecond auxiliary electrode 58 as a negative pole (or vice-versa). Incontrast to the pacing application, however, the controller 26 does notdeliver energy to the auxiliary electrodes 56, 58. Instead, anelectrical signal (typically a voltage measurement) progressing acrossthe auxiliary electrodes 56, 58 is monitored. For example, intrinsicelectrical activity across contacted tissue (e.g., a depolarizing wave)will progress from the first auxiliary electrode 56 to the secondauxiliary electrode 58 (or vice-versa). As the depolarizing waveprogresses from the first auxiliary electrode 56 to the second auxiliaryelectrode 58 (or vice-versa), the controller 26 (or anelectronically-linked analyzer) monitors or senses the changingelectrical signal(s), and can record or otherwise note variousattributes.

The optional vacuum source 28 can assume a variety of forms appropriatefor generating desired negative pressure levels. For example, the vacuumsource 28 can be a pump. Alternatively, a wall-mounted vacuum sourceconventionally available in many hospital operating rooms can beutilized.

The optional liquid source 30 can also assume any conventional form. Forexample, the liquid source 30 can be a flexible bag of liquid saline.Alternatively, a mechanized pump can be included.

The ablation system 20 can be employed to perform various tissueablation procedures. One such procedure relates to the treatment ofcardiac arrhythmia, and in particular atrial fibrillation, by forminglesions on epicardial tissue of the patient. With this in mind, FIG. 8is a simplified representation of the relevant anatomy of a patient(from an anterior perspective), reflecting a location of the heart Hrelative to the patient's chest C, including the sternum ST and ribcageR. A xiphoid process XP projects from the ribcage R. The heart H isarranged relative to the chest C such that right pulmonary veins RPVsand left pulmonary veins LPVs are posterior and superior. A posteriorview of the heart H is generally reflected in FIG. 9A, and illustratesthe right pulmonary veins RPVs and the left pulmonary veins LPVsentering into the top of the left atrium LA. The vena cava VC and aortaA are also shown. With these designations in mind, one cardiacarrhythmia treatment method entails, prior to use of the ablationinstrument 22 (FIG. 1), forming a first ablation lesion pattern 270 intothe left atrium LA around or encircling the left pulmonary veins LPVs(i.e., the junction of the left pulmonary veins LPVs with the leftatrium LA) and a second ablation lesion pattern 272 around the rightpulmonary veins RPVs as reflected in FIG. 9B. The first and secondablation patterns 270, 272 are commonly referred to as “islandpatterns,” and can be formed in various manners, for example via aclamp-type surgical ablation device available from Medtronic, Inc, underthe trade name Cardioblate® Gemini™. Regardless, the ablation instrument22 is then employed to form lesion patterns along epicardial tissue ofthe posterior left atrium LA that interconnects the islands 270, 272.

In particular, and with reference to FIG. 10A, an incision 280 is formedimmediately beneath the xiphoid process XP, thereby establishing asubxiphoid access or surgical approach to the heart H. As a point ofreference, the subxiphoid incision 280 may have been previously formed,for example in connection with the formation of the island ablationpatterns described above. The ablation instrument 22 is then manipulatedto position the head assembly 40 (FIG. 2) against the posterior leftatrium LA as shown in FIG. 10B. In particular, the head assembly 40 isinserted through the subxiphoid incision 280, and directed posteriorlyand superiorly about a posterior aspect of the heart H. The malleablenature of the tubular member 42 in some embodiments affords the surgeonthe ability to accommodate various anatomical obstacles presented by theparticular patient. Regardless, and as shown in FIG. 10C, the headassembly 40 is positioned such that the contact face 210 (hidden in FIG.10C, but shown, for example, in FIG. 3) abuts epicardial tissue of theposterior left atrium LA.

The vacuum source 28 (FIG. 1) is then activated. With the additionalreference to FIG. 10D, negative pressure is thereby established at thefirst and second suction regions 158, 160, drawing epicardial tissue Tof the posterior left atrium LA into intimate contact with thecorresponding ablation electrodes 52, 54. Though not fully illustratedin FIG. 10D, in some embodiments the skirts 152, 154 will elasticallycollapse or deflect in the presence of negative pressure in the suctionregions 158, 160, effectively establishing a consistent holding force ofthe epicardial tissue T along, and in intimate contact with, thecorresponding ablation electrodes 52, 54. The ablation electrodes 52, 54are evenly pressed against the targeted tissue T. The power source 24(FIG. 1) is then activated in a manner to deliver ablative energy to thefirst ablation electrode 52 for a time sufficient to ablate thecontacted tissue. The second ablation electrode 54 is sequentiallyenergized by the power source 24 for a time sufficient to ablatecontacted tissue. By providing the intimate, consistent or uniformcontact between the targeted tissue T and the ablation electrodes 52, 54as described above, predictable ablations (in terms of, for example,transmurality, conduction block, etc.) can be achieved. The ablationelectrodes 52, 54 can be sequentially operated in any order, or can besimultaneously energized. For safety purposes, the temperature of theablation electrodes 52, 54 can be closely monitored by the controller 26(FIG. 1), for example by electrical connection to the optionalthermocouples carried by the ablation electrode ends 176, 178, 180, 182(FIG. 5). The liquid source 30 (FIG. 1) can be simultaneously activatedto irrigate and cool the ablation electrodes 52, 54. For example, theliquid source 30 and the vacuum source 28 can be fluidly connected tothe head assembly 40 in tandem. The irrigation or cooling liquid (e.g.,cooled or room temperature saline) enters the suction regions 158, 160and cools the corresponding ablation electrode 52, 54; the now-heatedliquid is subsequently evacuated from the suction regions 158, 160 viathe suction apertures described above. Notably, when the head assembly40 is positioned at the target site (e.g., posterior left atrium) andsuction applied, the clinician can optionally perform a “hands-free”ablation, allowing the clinician to complete other tasks while theablation is taking place. Regardless, operation of the instrument 22results in first and second connective ablation lesions 290, 292 asshown in FIG. 10E.

The connective lesions 290, 292 interconnect the island patterns 270,272, thereby establishing a conductive block or “box” area 294 betweenjunctions of the left pulmonary veins LPVs and the right pulmonary veinsRPVs with the left atrium LA. As reflected in FIG. 10E, the necessarylength of the first connective lesion 290 (i.e., sufficient to extendfrom and between the first island 270 and the second island 272 at aninferior aspect thereof) corresponds with a length of the first ablationelectrode 52 (FIG. 4), whereas a length of the second connective lesion292 (i.e., sufficient to interconnect the first and second islands 270,272 along a superior aspect thereof) corresponds with a length of thesecond ablation electrode 54 (FIG. 4). Thus, the desired connectivelesions 290, 292 are formed by the ablation instrument 22 withoutrequiring movement of the head assembly 40 once the delivery of ablativeenergy has been initiated. In other embodiments, however, the ablationinstrument 22 can be operated to form a first segment of the first andsecond connective lesions 290, 292, and then moved transversely relativeto the heart H to form corresponding second segments of the connectivelesions 290, 292.

In some embodiments, the system 20 (FIG. 1) can further be operated toconfirm successful completion of the connective lesions 290, 292 (i.e.,that the conductive block 294 is electrically isolated). For example,the controller 26 (FIG. 1) can be operated, or caused to be operated, toperform pacing and/or sensing procedures immediately following deliveryof ablative energy to the ablation electrodes 52, 54. To this end, bydesirably positioning the auxiliary electrodes 56, 58 spatially betweenthe ablation electrodes 52, 54, the auxiliary electrodes 56, 58 willinherently be located “within” the confines of the conductive block 294.Thus, the auxiliary electrodes 56, 58 are properly located for desiredconduction block testing upon initial placement (i.e., immediately priorto ablating with the ablation electrodes 52, 54) of the contact face 210(FIG. 3) against the posterior left atrium LA; as such, testing can beperformed immediately following completion of the connective lesions290, 292, and the surgeon is not required to re-position the headassembly 40. With the head assembly 40 remaining in the same locationrelative to the epicardial tissue T (as in FIGS. 10C and 10D), thecontroller 26 operates the auxiliary electrodes 56, 58 in a bipolar modeto perform pacing test(s) (i.e., delivering the pacing energy asdescribed above). For example, as part of an exit block test, pacingenergy is applied “within” the conductive block 294 and an evaluation ismade as to whether or not the rest of the heart is “captured” inresponse. With some techniques, prior to ablating the connective lesions290, 292, a pacing energy sufficient to capture the heart is applied andthe corresponding power settings are recorded. The exit block test canthen consist of a determination as to whether the heart is “captured” atthe same power settings. When the heart cannot be captured using thesame pre-ablation power settings, an initial determination can be madethat the conductive block 294 was successful in isolating the targetsite. In other embodiments, if capture is not achieved at thepre-ablation power settings, the power output can then be increased(e.g., doubled) and a determination made as to whether the heart is“captured” at this increased power output. If capture is not achieved atthis double power heart pacing, the conductive block 294 can beconsidered to be isolated and exit blocking from this area proven.Conversely, where the heart is captured during the post-ablation exitblock test, an indication is given that the ablation lesion patterns270, 272, 290, 292 were not successful in isolating the target site 294,and the surgeon can then repeat the ablation procedure and/or formadditional lesion pattern(s) in other areas.

An entrance block test can also or alternatively be used to evaluate theeffectiveness of the ablation patterns 270, 272, 290, 292. Inparticular, the controller 26 (FIG. 1) operates the auxiliary electrodes56, 58 to sense electrical activity within the conductive block 294. Themonitored output may be recorded and saved as a visual “ECG” type outputand the collection of monitored information visually compared to eachother. Alternatively or in addition, an algorithm can be programmed tothe controller 26 and used to compare the captured output; if thedifference between the electrical activity prior to the ablation (e.g.,atrial P-wave) is reduced a significant amount (e.g., 80% reduction), itcan be assumed that the target site 294 has been successfully blocked.Conversely, if an insignificant difference is determined, additionallesion patterns can be formed. Additionally or alternatively, with theauxiliary electrodes 56, 58 being operated by the controller 26 in asensing mode, a pacing energy is applied to the heart outside of theconductive block region 294. If the auxiliary electrodes 56, 58(otherwise in contact with epicardial tissue inside of the conductiveblock 294) do not sense the so-applied pacing energy, it can bepositively concluded that entrance block has been achieved.

In some embodiments, the controller 26 (FIG. 1) can be programmed withset confirmation parameters and operate to automatically alert thesurgeon as to the results of the conduction block testing. For example,following ablation with the ablation electrodes 52, 54 (FIG. 3) asdescribed above, the controller 26 can automatically perform one or moreof the pacing/sensing tests. If the results of one or more of thesetests (e.g., the pre- and post-ablation atrial P-wave comparison testdescribed above) are viewed by the controller 26 as being indicative ofunsuccessful conduction block, the indicator device 260 (FIG. 2) isoperated to provide a warning to the surgeon (e.g., a red light).Conversely, when the controller 26 deems the test result(s) asimplicating successful conduction block, the indicator device 260 isoperated by the controller 26 to provide a confirmation to the surgeon(e.g., a green light). Other indicating techniques can be employed(e.g., graphical display, audible noise, etc.). Alternatively, theindicator device 260 can be omitted.

While the head assembly 40 (FIG. 3) has been described as having thefirst and second ablation electrodes 52, 54 (FIG. 3) with the shapesdescribed above, other configurations are also acceptable. For example,FIG. 11A is a simplified view of another head assembly 300 in accordancewith principles of the present disclosure and useful with the ablationinstrument 22 (FIG. 1). The head assembly 300 generally includes apaddle body 302, ablation electrodes 304 a-304 d, and auxiliaryelectrodes 306 a, 306 b. The paddle body 302 is sized and shaped for asubxiphoid surgical approach to the posterior left atrium, and can havethe wedge-like shape as shown. The electrodes 304 a-306 b are maintainedby, and are exteriorly exposed relative to a contact face 308 of, thepaddle body 302 in a spatially fixed manner. The ablation electrodes 304a-304 d are akin to the ablation electrodes 52, 54 described above andare segmented about (and in close proximity to) a perimeter of thepaddle body 302 a-302 d. The auxiliary electrodes 306 a, 306 b are akinto the auxiliary electrodes 56, 58 (FIG. 3) described above, and arelocated within a perimeter of the ablation electrodes 304 a-304 d forperforming pacing/sensing operations as described above. In otherembodiments, the auxiliary electrodes 306 a, 306 b can be omitted.During use, the contact face 308 is directed against targeted tissue andthe ablation electrodes 304 a-304 d sequentially energized to ablate aportion of a conductive block region, for example along epicardialtissue of the posterior left atrium between the left and right pulmonaryvein junctions to interconnect superior and inferior aspects ofseparately-formed island lesions. Other features described above (e.g.,suction regions, liquid supply/cooling, etc.) can be optionallyincorporated into the head assembly 300.

Another embodiment of a head assembly 310 in accordance with principlesof the present disclosure and useful with the ablation instrument 22(FIG. 1) is shown, in simplified form, in FIG. 11B. The head assembly310 includes a paddle body 312, primary ablation electrodes 314 a-314 d,a secondary ablation electrode 316, and auxiliary electrodes 318 a, 318b. The paddle body 312 is sized and shaped for delivery to the posteriorleft atrium via a subxiphoid surgical approach, and can have thewedge-like shape as shown. The electrodes 314 a-318 b are maintained by,and are exteriorly exposed relative to a contact face 320 of, the paddlebody 312 in a spatially fixed manner. The primary ablation electrodes314 a-314 d are segmented about (and in close proximity to) a perimeterof the paddle body 312, and are akin to the ablation electrodespreviously described. The secondary ablation electrode 316 is arrangedgenerally parallel with, but spaced from, the first primary ablationelectrode 314 a (i.e., a linear distance between the secondary ablationelectrode 316 and the fourth primary ablation electrode 314 d is lessthan a linear distance between the first primary ablation electrode 314a and the fourth primary ablation electrode 314 d). The auxiliaryelectrodes 318 a, 318 b are akin to the auxiliary electrodes describedabove, and are positioned within a perimeter defined by thesecond-fourth primary ablation electrodes 314 b-314 d and the secondaryablation electrode 316 for performing pacing/sensing protocols asdescribed above. In other embodiments, the auxiliary electrodes 318 a,318 b can be omitted. During use, the contact face 320 is directedagainst targeted epicardial tissue and the primary ablation electrodes314 a-314 d sequentially energized to create a portion of a conductiveblock lesion pattern, for example along epicardial tissue of theposterior left atrium between the left and right pulmonary veinjunctions to interconnect superior and inferior aspects ofseparately-formed island lesions. In instances where the anatomy of thepatient's heart is such that the first primary ablation electrode 314 ais too close to certain anatomical structures (e.g., the AV groove), thesecondary ablation electrode 316 can be energized instead of the firstprimary ablation electrode 314 a. Other features described above (e.g.,suction regions, liquid supply/cooling, etc.), can optionally beincorporated into the head assembly 310.

Another embodiment head assembly 330 in accordance with principles ofthe present disclosure and useful with the ablation instrument 22(FIG. 1) is shown, in simplified form, in FIG. 11C. The head assembly330 includes a paddle body 332, ablation electrodes 334 a-334 d, andauxiliary electrodes 336 a, 336 b. The paddle body 332 is akin to theconfigurations described above, and can have a generally wedge-likeshape for interfacing with the posterior left atrium via a subxiphoidsurgical approach. With the construction of FIG. 11C, however, opposingsides 338 a, 338 b of the paddle body 332 flare radially outwardly (ascompared to the shape of FIGS. 11A and 11B). Regardless, the electrodes334 a-336 b are maintained by, and exteriorly exposed relative to acontact face 340 of, the paddle body 332 in a spatially fixed manner.The ablation electrodes 334 a-334 d are akin to those above and aresegmented about (and in close proximity to) a perimeter of the paddlebody 332, including the flared edges 338 a, 338 b. With thisconstruction, when the contact face 340 is positioned against theposterior left atrium between the left and right pulmonary veinjunctions, the second and third ablation electrodes 334 b, 334 c aremore likely positioned to intersect with the pulmonary vein islandablation patterns (e.g., the island lesions 270, 272 of FIG. 9B). Theauxiliary electrodes 336 a, 336 b are akin to the auxiliary electrodesdescribed above, and can be operated to perform various pacing and/orsensing protocols. In other embodiments, the auxiliary electrodes 336 a,336 b can be omitted. Other features described above (e.g., suctionregions, liquid supply/cooling, etc.) can optionally be incorporatedinto the head assembly 330.

Yet another embodiment of a head assembly 350 in accordance withprinciples of the present disclosure and useful with the ablationinstrument 22 (FIG. 1) is shown, in simplified form, in FIG. 11D. Thehead assembly 350 includes a paddle body 352, ablation electrodes 354a-354 d, and auxiliary electrodes 356 a, 356 b. The paddle body 352 issized and shaped for delivery to the posterior left atrium via asubxiphoid surgical approach, and can have the generally oval-like shapereflected in FIG. 11D. The electrodes 354 a-356 b are maintained by, andexteriorly exposed relative to a contact face 358 of, the paddle body352 in a spatially fixed manner. The ablation electrodes 354 a-354 d aresegmented about (and in close proximity to) a perimeter of the paddlebody 352, and are otherwise akin to the ablation electrodes describedabove. The auxiliary electrodes 356 a-356 b are optional, and are akinto the auxiliary electrodes described above for performing one or morepacing/sensing protocols. During use, the contact face 358 is directedagainst targeted epicardial tissue and the ablation electrodes 354 a-354d sequentially energized to ablate a portion of a conductive blankregion, for example, along epicardial tissue of the posterior leftatrium between the pulmonary vein junctions to interconnect superior andinferior aspects of separately-formed island lesions. Other featuresdescribed above (e.g., suction regions, liquid supply/cooling, etc.) canoptionally be incorporated into the head assembly 350.

Yet another embodiment head assembly 360 in accordance with principlesof the present disclosure and useful with the ablation instrument 22(FIG. 1) is shown, in simplified form, in FIG. 11E. The head assembly360 includes a paddle body 362, ablation electrodes 364 a-364 c, a firstpair of auxiliary electrodes 366 a, 366 b and a second pair of auxiliaryelectrodes 368 a, 368 b. The paddle body 362 is sized and shaped fordelivery to the posterior left atrium via a subxiphoid surgicalapproach, and can have the wedge-like shape as shown. The electrodes 364a-368 b are maintained by, and are exteriorly exposed relative to acontact face 370 of, the paddle body 362 in a spatially fixed manner.The ablation electrodes 364 a-364 c are mounted to the paddle body 362in a segmented fashion, generally defining the Z-like pattern shown. Forexample, the first and third ablation electrodes 364 a, 364 c can begenerally parallel to one another, with the second ablation electrode364 b extending from the first ablation electrode 364 a at a first sideof the paddle body 362 to the third ablation electrode 364 c at anopposite side of the paddle body 362. The auxiliary electrode pairs 366a, 366 b, 368 a, 368 b are located at opposite sides of the secondablation electrode 364 b. With this construction, the contact face 370can be directed into contact with epicardial tissue of the posteriorleft atrium via a subxiphoid surgical approach, with the first and thirdablation electrodes 364 a, 364 c being sequentially energized to formlesions that interconnect superior and inferior aspects ofseparately-formed formed island ablation patterns as described above.The second ablation electrode 364 b also defines an ablation lesion,with the auxiliary electrode pairs 366 a, 366 b and 368 a, 368 b beingoperated to evaluate desired conduction block. Other features describedabove (e.g., suction regions, liquid supply/cooling, etc.) canoptionally be incorporated into the head assembly 360.

Another alternative head assembly 380 in accordance with principles ofthe present disclosure and useful with the ablation instrument 22(FIG. 1) is shown, in simplified form, in FIG. 11F. The head assembly380 includes a paddle body 382, ablation electrodes 384 a-384 c, a firstpair of auxiliary electrodes 386 a, 386 b and a second pair of auxiliaryelectrodes 388 a, 388 b. The head assembly 380 is highly akin to thehead assembly 360 (FIG. 11E) described above, with the paddle body 382being sized and shaped to access the posterior left atrium via asubxiphoid surgical approach. With the construction of FIG. 11F,however, the paddle body 382 has a clover-like shape with flared sides.The electrodes 384 a-388 b are maintained by, and exteriorly exposedrelative to a contact face 390 of, the paddle body 382 in a spatiallyfixed manner. The first and third ablation electrodes 384 a, 384 cextend along (and in close proximity to) portions of a perimeter of thepaddle body 382 as shown, with the second ablation electrode 384 bextending in the angular fashion shown (segmented from the first andthird ablation electrodes 384 a, 384 c). The auxiliary electrode pairs386 a, 386 b and 388 a, 388 b are arranged at opposite sides of thesecond ablation electrode 384 b, and are operable to perform variouspacing and sensing protocols. During use, the contact face 390 isdirected against target epicardial tissue and the ablation electrodes384 a-384 c sequentially energized to ablate a portion of a conductiveblock pattern, for example along epicardial tissue of the posterior leftatrium between the pulmonary vein junctions to interconnect superior andinferior aspects of separately-formed island ablation regions. Otherfeatures described above (e.g., suction regions, liquid supply/cooling,etc.) can optionally be incorporated into the head assembly 380.

Another embodiment head assembly 400 in accordance with principles ofthe present disclosure and useful with the ablation instrument 22(FIG. 1) is shown, in simplified form, in FIG. 11G. The head assembly400 includes a paddle body 402, ablation electrodes 404 a-404 f, andauxiliary electrodes 406 a, 406 b. The paddle body 402 is sized andshaped for delivery to the posterior left atrium via a subxiphoidapproach, and can have the clover-like shape shown. The electrodes 404a-406 b maintained by, and are exteriorly exposed relative to a contactface 410 of, the paddle body 402 in a spatially fixed manner. Theablation electrodes 404 a-404 f are mounted in a segmented fashion about(and in close proximity to) a perimeter of the paddle body 406. Finally,the auxiliary electrodes 406 a, 406 b are akin to the auxiliaryelectrodes described above, and are disposed within an area defined by apattern of the ablation electrodes 404 a-404 f. Alternatively, theauxiliary electrodes 406 a, 406 b can be omitted. With the clover-likeshape of the paddle body 402, upon placement of the contact face 410against epicardial tissue of the posterior left atrium between thepulmonary vein junctions, the second and seventh ablation electrodes 404b, 404 f are better positioned to more likely intersect with islandlesions as previously described. Other features described above (e.g.,suction regions, liquid supply/cooling, etc.) can optionally beincorporated into the head assembly 400.

Yet another embodiment head assembly 420 in accordance with principlesof the present disclosure and useful with the ablation instrument 22(FIG. 1) is shown, in simplified form, in FIG. 11H. The head assembly420 includes a paddle body 422, primary ablation electrodes 424 a-424 d,secondary ablation electrodes 426 a-426 d, and auxiliary electrode pairs428 a-428 e. The paddle body 422 is sized and shaped for delivery to theposterior left atrium via a subxiphoid surgical approach, and can havethe wedge-like shape shown. The electrodes 424 a-428 e are maintainedby, and are exteriorly exposed relative to a contact face 430 of, thepaddle body 422 in a spatially fixed manner. The primary ablationelectrodes 424 a-424 d are mounted in a segmented fashion about (and inclose proximity to) a perimeter of the paddle body 422. The secondaryablation electrodes 426 a-426 d extend generally parallel with the firstprimary ablation electrode 424 a in a spaced apart fashion. Respectiveones of the auxiliary electrode pairs 428 a-428 e are arranged as shown.During use, the contact face 430 is directed against targeted epicardialtissue and some or all of the ablation electrodes 424 a-424 d and 426a-426 d are sequentially energized to ablate corresponding lesionpatterns, for example at the posterior left atrium to interconnectsuperior and inferior aspects of separately-formed pulmonary vein islandlesions. Various ones of the auxiliary electrode pairs 428 a-428 e canbe selectively operated to perform various pacing and sensing protocolsto evaluate conduction blockage of the resultant lesion pattern.Alternatively, one or more of the auxiliary electrode pairs 428 a-428 ecan be omitted. Other features described above (e.g., suction regions,liquid supply/cooling, etc.) can optionally be incorporated into thehead assembly 420.

Another head assembly 440 in accordance with principles of the presentdisclosure and useful with the ablation instrument 22 (FIG. 1) is shown,in simplified form, in FIG. 11I. The head assembly 440 includes a paddlebody 442, ablation electrodes 444 a-444 d, and an auxiliary electrodepair 446 a-446 b. The paddle body 442 is sized and shaped for deliveryto the posterior left atrium via a subxiphoid surgical approach, and canhave the wedge-like shown. In contrast to other embodiments, opposingsides 448 a, 448 b of the paddle body 442 have a concave shape. Withthis construction, the opposing sides 448 a, 448 b may more readily titbetween the right and left pulmonary vein junctions, for example withthe left atrium. Regardless, the electrodes 444 a-446 b are maintainedby, and are exteriorly exposed relative to a contact face 450 of, thepaddle body 442 in a spatially fixed manner. The ablation electrodes 444a-444 d are akin to previous embodiments, and are mounted in a segmentedfashion about (and in close proximity to) a perimeter of the paddle body442. The auxiliary electrodes 446 a-446 d are also akin to otherembodiments, and are generally disposed within a pattern defined by theablation electrodes 444 a-444 d. The head assembly 440 can be operatedin a manner akin to previous descriptions, with the contact face 450being directed against targeted epicardial tissue, for example along theposterior left atrium between the pulmonary vein junctions and theablation electrodes 444 a-444 d sequentially energized to ablate aportion of a conductive block pattern, for example interconnectingsuperior and inferior aspects of separately-formed island ablationregions. Other features described above (e.g., suction regions, liquidsupply/cooling, etc.) can optionally be incorporated into the headassembly 440.

Yet another embodiment head assembly 460 in accordance with principlesof the present disclosure and useful with the ablation instrument 22(FIG. 1) is shown, in simplified form, in FIG. 11J. The head assembly460 includes a paddle body 462, ablation electrodes 464 a, 464 b andauxiliary electrodes 466 a, 466 b. The paddle body 462 is sized andshaped for delivery to the posterior left atrium via a subxiphoidsurgical approach. With the construction of FIG. 11J, a trailing region468 of the paddle body 462 forms or defines transverse protrusions 470a, 470 b. The protrusions 470 a, 470 b are generally configured tocontact or engage one of the left pulmonary veins and one of the rightpulmonary veins, respectively, when the head assembly 460 is otherwisepositioned along the posterior left atrium. Thus, the protrusions 470 a,470 b serve to better ensure desired arrangement of the head assembly460 along the posterior left atrium. The electrodes 464 a-466 b aremaintained by, and exteriorly exposed relative to a contact face 472 of,the paddle body 462 in a spatially fixed manner. The ablation electrodes464 a, 464 b are akin to previous embodiments, and are arranged in aspaced apart fashion. The auxiliary electrode 466 a, 466 b are akin toprevious embodiments, and are mounted to the paddle body 462 between theablation electrodes 464 a, 464 b. During use, the contact face 472 isdirected into contact with epicardial tissue of the posterior leftatrium, with the protrusions 470 a, 470 b engaging respective ones ofthe left and right pulmonary veins. The ablation electrodes 464 a, 464 bare sequentially energized to ablate a portion of a conductive blockpattern, for example interconnecting superior and inferior aspects ofseparately-formed island ablation regions as described above. Whereprovided, the auxiliary electrodes 486 a, 486 b are employed to performvarious pacing/sensing protocols. Other features described above (e.g.,suction regions, liquid supply/cooling, etc.) can optionally beincorporated into the head assembly 460.

Another embodiment head assembly 480 in accordance with principles ofthe present disclosure and useful with the ablation instrument 22(FIG. 1) is shown, in simplified form, in FIG. 11K. The head assembly480 includes a paddle body 482, ablation electrodes 484 a, 484 b, andauxiliary electrodes 486 a, 486 b. The paddle body 482 is sized andshaped for delivery to the posterior left atrium via a subxiphoidsurgical approach, and can have the wedge-like shape shown. Theelectrodes 484 a-486 b are maintained by, and are exteriorly exposedrelative to a contact face 488 of, the paddle body 482 in a spatiallyfixed manner. The ablation electrodes 484 a, 484 b extend in a generallyparallel fashion at opposite ends of the paddle body 482, and theauxiliary electrodes 486 a, 486 b are located between the ablationelectrodes 484 a, 484 b. The head assembly 480 is operable in mannerssimilar to those described above, with the contact face 488 beingdirected against epicardial tissue of the posterior left atrium betweenthe pulmonary vein junctions. The ablation electrodes 484 a, 484 b aresequentially energized to ablate a portion of a conductive blockpattern, for example interconnecting superior and inferior aspects ofseparately-formed island ablation regions. The auxiliary electrodes 486a, 486 b can be used for various pacing/sensing protocols, but can beomitted. Other features described above (e.g., suction regions, liquidsupply/cooling, etc.) can optionally be incorporated into the headassembly 480.

Another embodiment head assembly 490 in accordance with principles ofthe present disclosure and useful with the ablation device 22 (FIG. 1)is shown, in simplified form, in FIG. 11L. The head assembly 490includes a paddle body 492, ablation electrodes 494 a, 494 b, andauxiliary electrodes 496 a, 496 b. The paddle body 492 is sized andshaped for delivery to the posterior left atrium via a subxiphoidsurgical approach, and can have the oval-like shape shown. Theelectrodes 494 a-496 b are maintained by, and are exteriorly exposedrelative to a contact face 498 of, the paddle body 492 in a spatiallyfixed manner. The ablation electrodes 494 a, 494 b extend in a generallyparallel fashion at opposite ends of the paddle body 492. The auxiliaryelectrodes 496 a, 496 b are mounted to the paddle body 492 between theablation electrodes 494 a, 494 b. The head assembly 490 is operable toperform various ablation procedures as described above, including thecontact face 498 being directed against epicardial tissue of theposterior left atrium between the pulmonary vein junctions. The ablationelectrodes 496 a, 496 b are sequentially energized to ablate a portionof a conductive block pattern, for example interconnecting superior andinferior aspects of separately-formed island ablation regions. Theauxiliary electrodes 496 a, 496 b can be used for various pacing/sensingprotocols, but can be omitted. Other features described above (e.g.,suction regions, liquid supply/cooling, etc.) can optionally beincorporated into the head assembly 490.

Another embodiment head assembly 500 in accordance with principles ofthe present disclosure and useful with the ablation device 22 (FIG. 1)is shown, in simplified form, in FIG. 11M. The head assembly 500includes a paddle body 502, ablation electrodes 504 a, 504 b, andauxiliary electrodes 506 a, 506 b. The paddle body 502 is sized andshaped for delivery to the posterior left atrium via a subxiphoidsurgical approach, and can have the generally circular shape shown. Theelectrodes 504 a-506 b are maintained by, and are exteriorly exposedrelative to a contact face 508 of, the paddle body 502 in a spatiallyfixed manner. The ablation electrodes 504 a, 504 b are arranged in asegmented fashion about (and in close proximity to) a perimeter of thepaddle body 502. The auxiliary electrodes 506 a, 506 b are locatedbetween or circumscribed by the ablation electrodes 504 a, 504 b. Thehead assembly 500 is operable in manners similar to those describedabove, with the contact face 508 being directed against epicardialtissue of the posterior left atrium between the pulmonary veinjunctions. The ablation electrodes 504 a, 504 b are sequentiallyenergized to ablate a corresponding lesion pattern, for example a lesionpattern interconnecting separately-formed pulmonary vein island lesions.The auxiliary electrodes 506 a, 506 b can be operated to perform variouspacing and/or sensing procedures, or can be omitted. Other featuresdescribed above (e.g., suction regions, liquid supply/cooling, etc.) canoptionally be incorporated into the head assembly 500.

Another embodiment head assembly 510 in accordance with principles ofthe present disclosure and useful with the ablation device 22 (FIG. 1)is shown, in simplified form, in FIG. 11N. The head assembly 510includes a paddle body 512, ablation electrodes 514 a-514 c, andauxiliary electrodes 516 a, 516 b. The paddle body 512 is sized andshaped for delivery to the posterior left atrium via a subxiphoidsurgical approach, and can have the wedge-like shape shown. Theelectrodes 514 a-516 b are maintained by, and are exteriorly exposedrelative to a contact face 518 of, the paddle body 512 in a spatiallyfixed manner. The ablation electrodes 514 a-514 c are arranged in asegmented fashion, defining a C-like pattern as shown. The auxiliaryelectrodes 516 a, 516 b are located along the paddle body 512essentially within the C-like pattern. The head assembly 510 can beemployed to perform various ablation and other procedures in waysconsistent with previous descriptions, including the contact face 518being directed against epicardial tissue of the posterior left atriumbetween the pulmonary vein junctions. The ablation electrodes 514 a-514c are sequentially energized to ablate a portion of a conductive blockpattern, for example interconnecting superior and inferior aspects ofseparately-formed island lesions. Other features described above (e.g.,suction regions, liquid supply/cooling, etc.) can optionally beincorporated into the head assembly 510.

Another embodiment head assembly 520 in accordance with principles ofthe present disclosure and useful with the ablation device 22 (FIG. 1)is shown, in simplified form, in FIG. 11O. The head assembly 520includes a paddle body 522, primary ablation electrodes 524 a-524 c,secondary ablation electrodes 526 a-526 c, a first auxiliary electrodepair 528 a, 528 b, and a second auxiliary electrode pair 530 a, 530 b.The paddle body 522 is sized and shaped for delivery to the posteriorleft atrium via a subxiphoid surgical approach, and can have the wide,wedge-like shape shown. In particular, the paddle body 522 definesopposing sides 532 a, 532 b, with the first side 532 a being longer thanthe second side 532 b. The electrodes 524 a-530 b are maintained by, andare exteriorly exposed relative to a contact face 534 of, the paddlebody 522 in a spatially fixed manner. The primary ablation electrodes524 a-524 c are arranged in the Z-like pattern shown. The secondaryablation electrodes 526 a-526 c are also mounted to the paddle body 522in a segmented fashion, but extend along the first side 532 a. With thisarrangement, upon deployment of the head assembly 520 along theposterior left atrium, the secondary ablation electrodes 526 a-526 c canbe energized to create a lesion pattern between the superior vena cavaand the inferior vena cava. Stated otherwise, the head assembly 520 canbe employed to form connective lesions between the superior and inferioraspects of separately-formed pulmonary vein island lesions as previouslydescribed, whereas the secondary ablation electrodes 526 a-526 c areutilized, with corresponding re-positioning of the contact face 534, todefine another portion of the MAZE pattern. Regardless, the auxiliaryelectrode pairs 528 a, 528 b and 530 a, 530 b are operable in mannersakin to previous descriptions for performing various pacing and/orsensing operations. Other features described above (e.g., suctionregions, liquid supply/cooling, etc.) can optionally be incorporatedinto the head assembly 520.

Another embodiment head assembly 540 in accordance with principles ofthe present disclosure and useful with the ablation device 22 (FIG. 1)is shown, in simplified form, in FIG. 11P. The head assembly 540includes a paddle body 542, primary ablation electrodes 544 a, 544 b,secondary ablation electrodes 546 a, 546 b, tertiary ablation electrodes548 a, 548 b, and three pairs of auxiliary electrodes 550 a-550 c. Thepaddle body 542 is sized and shaped for delivery to the posterior leftatrium via a subxiphoid surgical approach, and can have thecircular-like shape shown. The electrodes 544 a-550 c are maintained by,and are exteriorly exposed relative to a contact face 552 of, the paddlebody 542 in a spatially fixed manner. The primary electrodes 554 a, 554b are arranged in a segmented fashion at a perimeter of the paddle body542. Thus, the primary ablation electrodes 544 a, 544 b define acircle-like pattern. The secondary ablation electrodes 546 a, 546 b arealso arranged in a segmented fashion to define a circular-like pattern,but are located within, and spaced from, the primary ablation electrodes544 a, 544 b. The tertiary ablation electrodes 548 a, 548 b are within,and spaced from, the circular pattern of the secondary ablationelectrodes 546 a, 546 b. Finally, the auxiliary electrode pairs 560a-560 c are mounted to the paddle body 542 between the circular patternsof the ablation electrodes 544 a-548 b as shown. Desired lesion patternscan be generated by directing the contact face 552 against targetedepicardial tissue of the posterior left atrium and sequentiallyenergizing respective ones of the ablation electrode 544 a-548 d. Forexample, the primary ablation electrodes 544 a, 544 b can be energizedto form a lesion pattern that interconnects superior and inferioraspects of separately-formed pulmonary vein island lesions. Theauxiliary electrode pairs 560 a-560 c are operable in manners akin tothose previously described, facilitating various pacing and/or sensingprocedures. Other features described above (e.g., suction regions,liquid supply/cooling, etc.) can optionally be incorporated into thehead assembly 540.

Another embodiment head assembly 570 in accordance with principles ofthe present disclosure and useful with the ablation device 22 (FIG. 1)is shown, in simplified form, in FIG. 11Q. The head assembly 570includes a paddle body 572, ablation electrodes 574 a-574 c, andauxiliary electrodes 576 a, 576 b. The paddle body 572 is sized andshaped for delivery to the posterior left atrium via a subxiphoidsurgical approach, and can have the wedge-like shape shown. In addition,the paddle body 572 forms or defines a cooling zone 578, for example asan internal pocket within the paddle body 572. Tubing 580 is fluidlyconnected to the cooling zone 578, and serves to deliver a coolingliquid (e.g., saline) to the cooling zone 578. The electrodes 574 a-576b are maintained by, and exteriorly exposed relative to a contact face582 of, the paddle body 572 in a spatially fixed manner. The ablationelectrodes 574 a-574 d are arranged along (and in close proximity to) aperimeter of the paddle body 572. The auxiliary electrodes 576 a, 576 bare located along the paddle body 572 within a pattern defined by theablation electrodes 574 a-574 c. During use, the head assembly 570 isoperable in manners akin to those previously described, with the contactface 582 being directed against targeted epicardial tissue of theposterior left atrium between the pulmonary vein junctions. The ablationelectrodes 574 a-574 d are sequentially energized to ablate a desiredlesion pattern into contacted tissue. The auxiliary electrodes 576 a,576 b facilitate the performance of various pacing and/or sensingprocedures. In addition, a cooling liquid can be provided to and/orcirculate within the cooling zone 578 as desired to effectuate coolingof contacted anatomy (e.g., the circumflex artery).

Another embodiment head assembly 590 in accordance with principles ofthe present disclosure and useful with the ablation device 22 (FIG. 1)is shown, in simplified form, in FIG. 11R. The head assembly 590includes a paddle body 592, ablation electrodes 594 a-594 c, and twopairs of auxiliary electrodes 596 a, 596 b. The paddle body 592 is sizedand shaped for delivery to the posterior left atrium via a subxiphoidsurgical approach, and can have the wedge-like shape shown. Theelectrodes 594 a-596 b are maintained by, and are exteriorly exposedrelative to a contact face 598 of, the paddle body 592. The ablationelectrodes 594 a-594 c are arranged in the Z-like pattern shown. In thisregard, skirts 600 a-600 c are formed or provided about respective onesof the ablation electrodes 594 a-594 c, and establish correspondingsuction regions 602 a-602 c. A negative pressure source (not shown) isfluidly connected to each of the suction regions 602 a-602 c; uponapplication of negative pressure, tissue otherwise in contact with theskirts 600 a-600 c is pulled or suctioned into intimate contact with thecorresponding ablation electrodes 592 a-592 c. Thus, operation of thehead assembly 590 in performing an ablation procedure is akin toprevious descriptions, including the contact face 598 being directedagainst targeted epicardial tissue of the posterior left atrium betweenthe pulmonary vein junctions. Tissue to be ablated is suctioned intocontact with the selected ablation electrode 592 a-592 c andsequentially ablated. The auxiliary electrode pairs 596 a, 596 b areoperable in manners akin to previous descriptions, and can facilitatevarious pacing and/or sensing procedures.

The ablation instruments, systems, and methods of the present disclosureprovide a marked improvement over previous designs. By promoting readyaccess to, and ablative contact with, epicardial tissue of the posteriorleft atrium via a subxiphoid surgical approach, procedures can beperformed in ways not heretofore available. The subxiphoid approach is amidline skin incision that avoids the division of major muscle groups orbone. The incision is made inferior to the sternum, such that the extentof the incision is primarily a cosmetic concern and is withoutlimitation from surrounding bone. The surgeon has the choice of how longof an incision to apply in order to achieve proper visibility of thetargeted tissue site. The incision may be easily widened using standardand/or long blade retractors. Regardless, a desired portion of a MAZElesion pattern is easily formed with the ablation instrument of thepresent disclosure, forming desired posterior aspect pulmonary veinisland lesion interconnections. Further, in some embodiments, aso-formed conduction block can be readily evaluated with the ablationinstrument.

Although the present disclosure has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges can be made in form and detail without departing from the spiritand scope of the present disclosure.

1-28. (canceled) 29: An ablation instrument for applying ablative energyto tissue, the ablation instrument comprising: a head assembly defininga tissue contact face and including: first and second ablationelectrodes exteriorly exposed at the tissue contact face; a first skirtprojecting from the tissue contact face and completely surrounding aperimeter of the first ablation electrode to define a first suctionregion; a second skirt projecting from the tissue contact face andcompletely surrounding a perimeter of the second ablation electrode toestablish a second suction region; wherein the second skirt does notsurround the first suction region and the first skirt does not surroundthe second suction region; a first suction aperture formed by the tissuecontact face within the first suction region for applying a suctionforce to the first suction region; and a second suction aperture formedby the tissue contact face within the second suction region for applyinga suction force to the second suction region. 30: The ablationinstrument of claim 29, wherein the instrument is manipulable to locatethe tissue contact face on epicardial tissue between left and rightpulmonary vein junctions of a patient's posterior left atrium via asubxiphoid surgical approach. 31: The ablation instrument of claim 29,wherein the instrument is manipulable to locate the first and secondablation electrodes on epicardial tissue between left and rightpulmonary vein junctions of a patient's posterior left atrium via asubxiphoid surgical approach. 32: The ablation instrument of claim 29,further comprising: a tubular member extending from the head assembly.33: The ablation instrument of claim 32, wherein a maximum diameter ofthe tubular member is less than a maximum width of the head assembly.34: The ablation instrument of claim 32, wherein the first and secondablation electrodes are arranged to extend generally perpendicular to acentral axis of the tubular member. 35: The ablation instrument of claim32, further comprising: one or more suction lumens fluidly connected toeach of the suction apertures and extending through the tubular member.36: The ablation instrument of claim 32, further comprising: wiringelectrically connected to the first and second ablation electrodes fordelivering energy to the first and second ablation electrodes, thewiring extending through the tubular member. 37: The ablation instrumentof claim 29, further comprising: a negative pressure source fluidlyconnected to the suction apertures via one or more suction lumens. 38:The ablation instrument of claim 29, wherein the first and secondablation electrodes are configured such that when the head assembly ispositioned along the posterior left atrium between left and rightpulmonary veins, the ablation electrodes are operable to form lesionsinterconnecting island lesions surrounding junctions of the pulmonaryveins with the left atrium. 39: The ablation instrument of claim 29,wherein the head assembly further includes: first and second auxiliaryelectrodes exteriorly exposed at the contact face, wherein the auxiliaryelectrodes are electrically isolated from one another and are locatedbetween the first and second ablation electrodes. 40: The ablationinstrument of claim 39, wherein the auxiliary electrodes are operable toperform a pacing operation on a patient's heart. 41: The ablationinstrument of claim 39, wherein the auxiliary electrodes are operable tosense electrical activity on a patient's heart.